Influence of air pollution on the nutritional status of Navarraʹs Forests, Spain

During a two year research period from 1992 to 1993, foliage samples from different tree species were taken in 17 forest stands located in Navarra, Spain. Samples were analyzed for Ca, Cd, Cu, Fe, K, Mg, Mn, N, Na, P, Pb, S and Zn. The health of the sampling trees was assessed by determining the degree of defoliation and discolouration of the canopies. In almost all the species, no significant correlations between the different foliar elements and the crown condition parameters were observed, although in Quercus faginea trees, an increase of defoliation was associated with an increase in P and S concentrations. In general, the nutritional status of the sampled trees was good. However, when forest stands of the same species were compared, higher lead and cadmium concentrations were detected respectively in Goizueta (1) and Larra (11) stands, fact that suggests an anthropogenic influence of pollutants in such areas.